Emergency devices such as emergency lighting for use in buildings and the like are each provided with an autonomous and self-diagnostic capability so that the light can be tested to ensure that it will operate in an emergency situation in the event of loss of power to a building. Typically, tests take place on a routine basis such as a monthly and annual basis. In Australia, standards prescribe tests on a six monthly basis. Data is sent back to a central server for analysis and display so that if a failure is detected, appropriate repairs or replacement can take place.
The emergency devices are usually connected to the central server by a cable such as a twisted pair cable. Such wiring is bulky and not easy to install in old buildings.